1. Technical Field
The present invention relates to a method of manufacturing an organic EL element, an organic EL element, an organic EL apparatus provided with the organic EL element, and an electronic device.
2. Related Art
An organic electro-luminescence (EL) element has a functional layer including a luminescence material consisting of an organic compound between an anode and a cathode. As a method of forming such a functional layer, a vapor phase process such as a vacuum deposition method (also referred to as a dry process) and a liquid phase process using a solution in which a functional layer forming material is dissolved or dispersed in a solvent (also referred to as a wet process or a coating process) are known. Generally, a low molecular material is suitably used in the vapor phase process and a high molecular material is used in the liquid phase process from the viewpoint of film forming properties. It is known that the high molecular material is inferior in terms of the luminescent efficiency and the luminescent lifetime in some cases, compared to the low molecular material. On the other hand, since the organic EL element can relatively easily be formed on a large substrate, compared to the vapor phase process, the liquid phase process has been continuously developed.
For example, in JP-A-2006-190759, an organic EL element in which a hole injection and transport layer is a high molecular hole injection and transport layer obtained by forming a film using a high molecular material by a wet process and a luminescence layer is a low molecular luminescence layer obtained by forming a film using a low molecular luminescence material by a wet process is disclosed. As the low molecular luminescence material, an asymmetric low molecular compound having an anthracene skeleton or a pyrene skeleton is included.
In addition, for example, in JP-A-2011-233855, a method of manufacturing an organic EL display apparatus having a first organic EL element of blue color and a second organic EL element of other colors and a method of forming a second organic luminescence layer of the second organic EL element by an coating process using a mixed material including a low molecular material and a high molecular material are disclosed. According to JP-A-2011-233855, as a low molecular material, for example, a monomer having a weight average molecular weight of 50,000 or less is included.
In JP-A-2006-190759 describe above, as a method of forming the luminescence layer, an example of forming a film using a toluene solution including 1 wt % of the low molecular luminescence material by a spin coat method to form the luminescence layer in which the luminescence of blue color can be obtained is described. However, in a case where the organic EL element is applied to pixels of a flat display panel, it is necessary to produce the organic EL element in which the luminescence of not only blue color but also red color, green color, and the like can be obtained on a substrate. That is, the need for separately applying a solution, selectively, including the low molecular luminescence material corresponding to the pixels of each color arises. In doing so, there is a problem in which an aggregation of the low molecular material occurs in a region which is separately applied, selectively, and thus a coating unevenness easily occurs, compared to a case of forming a film by applying a solution onto an entire surface of the substrate such as a spin coat method.
On the other hand, in JP-A-2011-233855, as a method of selectively applying a solution or a dispersion liquid including a mixed material mixing the low molecular material and the high molecular material, a liquid droplet discharging method such as an ink jet method or a nozzle coat method is included. In addition, in JP-A-2011-233855, though the weight average molecular weight of the low molecular material is set to 50,000 or less, there is a request for using the low molecular material having even smaller weight average molecular weight in order to further improve the luminescent efficiency and the luminescent lifetime of the organic EL element. That is, a method of manufacturing the organic EL element in which both film forming properties in separately applying a solution, selectively, and characteristics required after forming a film can be achieved is required.